Process of making friction facings



Patented May 6, 1924.-

v v 1. 93. UNITED STATES PATENT OFF-ICE.

C. STANLEY, OF B RIDGEIPORT, CONNECTICUT, ASSIGNOR TO RAYBESTOS COMPANY, OF BRIDGEPORT, CONNECTICUT, A! CORPORATION OF CONNECTICUT. I

Pnoonss or MAKING rnrc'rron names No Drawing. Application filed September 24, 1919, Serial No. 325,914. Renewed October 28, ,1921." Serial To all whom it may concern: Be it known that I, FREDERICK C. STAN- LEY, a citizen of the United States, residing in ,thecity of Bridgeport, county of Fairfield, and State of Connecticut, have invented certain new and useful Improvements in Processes of Makin Friction Facings, of which the following is a specification.

This invention relates to improvements in rocess of making friction facings and reers more particularly to a' clutch facing'or brake lining adapted for use in motor vehicles. I i

The-inventionis directed to a novel ro'c- 'ess of making a friction facing from elted unwoven asbestos fibre saturated with a binder.

The object of the invention is to provide a process by which" the friction facing has a maximum tensile strength and hardness.

so thatit can withstand the shocks to which these' facings 'are subjected in a motor car and also will have suflicient resistance to abrasion; while at the same time it has the proper co-eflicient of friction. It is also necessary that the binder in these facings must be unaffected by oilor water in use,

which object is accomplished by the present invention without in any way detracting from the other characteristics.

A product similar to that made by this process is disclosed and claimed in applicants co-pendingapplication, Serial No.- 405,507.

The process may be carried out as fol- :lows: Asbestosfibre preferably the short or ow grin ng machine or cutter. The ground material is then put into a beater mixed with the water or other solution and beaten into a pulp. The pulp is then delivered to a paper making machine as for example a wet board machine and formed into sheets or boards of suitable width and thickness. This forms an unwoven felted sheet.

As a feature of the invention, there is mixed with the pulp in the beater an oxidiz-' ing agent, as for example borate of manganese. In using borate of manganese as an oxidizing agent, the amount employed is approximately 1.6 per cent by the weight of the asbestos fibre although this dan be varied according to the characteristics of the product desired. This oxidizing agent faciligrade fibre is first ground in a suitable to three minutes.

tates or hastens the cure of the binder and It also tendsto produce a uniform curing. throughout the mass during the curing operation herein? after described. It is to be noted that this reagent is put into the pulp before the for-' mation of the sheet and not during the w After the sheets or boards have been formed as described, they are subjected to hydraulic pressure in suitable presses and saturating and curing steps of the process.-

are then hung'up to dry in a' drying room of sufiicient temperature to' remove the water. The sheet is then calendered to the desired thickness and the friction facings are then cut out of the sheet. The sheets are subjected to sufiicient pressure in the calender to obtain as much tensile strength in the dry sheet as isfeasible. The friction facings whether clutch rings or brake. 'linsaturating tank is filled with a binder. This binder may consist of 94 per cent of linseed oil, 6 per cent of gilsonite in the solution in the oil thinned with gasoline to about 33 Baum gravity. The friction facin 's are then immersed while suspended on -su1table rods "in this binder solution for a period of half an hour. The friction facings are now ready for. saturation. The

ings are then removed and put 'in a closed steam oven and maintained at a temperature of about-200 F. to drive off the gasoline which gasoline may be recovered and saved. This steam treatment is preferably continued from twoto three hours.

The friction facings are then removed to a closed baking oven where they are subjected to a temperature of about 250 F., for a period of'twelve hours. The facings are then taken out ofthe oven and immersed in another saturating'tank containing a solution of 66 per cent of linseed oil and 33 per cent of gasoline, the gravity of the solution being about 33 Baum. This second immersion takes place for from two In both of thesaturating steps double boiled linseed oil is preferable. The friction facings are then put into a second closed baking oven and maintained at a temperature of 300 F. for

twenty four hours. The heat in both of the baking ovens is preferably dry heat.

The friction facings are then removed from the second oven and sand papered to micrometer size and to get a smooth finish to the facing. The facings are now ready for use.

I have given above an illustration in which the process is actually carried out in commercial. operation. It is to be understood that the temperature and length of treatment are subject to reasonable variations depending on the flexibility and strength required in the finished product. Also oils other than linseed oil may perhaps in certain cases be used and other asphalts substituted for gilsonite.

During the baking operation, the linseed oil, due to the presence of the water in the oven and also to the oxidizing agent of the sheet is oxidized to produce a tough hard binder. The solubility of the linseed oil in the gasoline before the baking treatments is practically 100%, while after the baking treatments it is very materially reduced and in fact the baking operation may be so carried out as to make the oil practically .insoluble in the gasoline. It is to be noted that by means of the double saturation and double baking, a more efiicient curing of the binder is obtained and the sheet can be impregnated with larger quantities of binder. This adds-greatly to the tensile strength and hardness of the finished product. In order that the tensile strength of the friction facings made in this mannermay be more clearly understood, I submit the followin table in giving actual tests made on such riction facings:

' Average ten- Average Thickness of Thickness of sheet belore sheet alter gi g gflg ggggf calendaring calendaring facing in lbs r b in inches. in inches. per sq. in Bri i o. 150 I o. m 4, 614 23. 4 145 123 4, 282 17. 2- 1&0 1% 4, 028 16. 6 135 123 3, 966 15. 3

The strength and hardness of the product made by thisprocess is far in excess, in fact from 1000 to 2000 lbs., upwards in tensile strength, over that heretofore obtained from any unwoven saturated friction facing and is even stronger than a woven sheet. The hardness also is proportionately increased over the friction facings heretofore made. It is to be noted that in the baking operation, the reaction develops autogenous heat or in other words exo-thermic and care must be take to prevent the material from becoming so highly heated as to catch fire. This tion facings therefrom, subjecting the facings to a plurality of saturations in an oxidizable binder, subjecting them to a baking operation after each saturation, said baking operations being carriedout at a tempera ture sufliciently high to cause oxidation of the binder.

2. A process of making a friction facing consisting in mixin borate of manganese with asbestos pulp, ormingunwoven sheets therefrom, cutting friction facings from the sheets, subjecting them to a plurality of saturations in an oxidizable binder, subjecting them to a baking operation after each saturation, said baking operations being carried out at a temperature sufliciently high to cause an oxidation of the binder.

3. A process of making a friction facing which consists in subjecting a facing having 'a substantially incombustible wearing surface and containing borate of manganese, to saturation in an oxidizable binder and in then baking the facing.

4. The process of making a friction facing, compgising subjecting the facing having a su tantially incombustible wearing surfaeeand containin borate of manganese. to saturation in an oxidizable binder and in then heating the facin p FREDERIEK C. STANLEY. 

